The present invention relates to the field of motor vehicle internal combustion engines and in particular proposes an inlet manifold.
As is known, the inlet manifold of an internal combustion engine has the task of distributing an inlet flow across all the cylinders of the engine. This inlet flow comes either directly from outside, after simple filtration, and is therefore air, or from a mixture of fresh air and of exhaust gases, metered in this case by an EGR valve. The inlet manifold of an internal combustion engine has to be permeable enough that it guarantees the performance of the internal combustion engine. A certain level of permeability therefore needs to be achieved. This level of permeability is obtained by taking the mean of the permeabilities across all the tracts associated with the various cylinders of the engine when one tract is delivering. However, each tract has to have a permeability similar to the permeabilities of the other tracts so as not to place one cylinder at an advantage or at a disadvantage in relation to the others because this would lead to malfunctioning of the internal combustion engine or would involve the internal combustion engine having to have downgraded settings.
In the case of internal combustion engines, it is known that motor manufacturers are looking to generate an aerodynamic movement of the tumble type (a helicoidal tumbling movement of the inlet flow in the cylinder of the engine and the axis of rotation of which is perpendicular to the axis of the cylinder). This movement, created mainly by the shape of the inlet ducts of the internal combustion engine, consists in encouraging flow over the front of the inlet valves, which corresponds to so-called “conventional” tumble or over the rear of the inlet valves, which corresponds to so-called “reverse” tumble. It is therefore appropriate to ensure that the geometry of the inlet manifold does not cause this level of tumble to drop and does not create any dispersion in the tumble-type movement. Such phenomena could arise particularly when the distribution of the inlet flow leaving the various ducts or tracts of the inlet manifold becomes sufficiently inhomogeneous and disrupts the distribution of the desired velocity of the inlet flow around the inlet valves.
The present-day solutions propose inlet manifolds consisting of an inlet flow inlet duct, the inlet duct being open at one end to allow the inlet flow to pass, and closed at the other end and opening on its lateral surface onto a plurality of identical outlet ducts the axes of symmetry of which are perpendicular to the axis of symmetry of the inlet duct and mutually parallel, each outlet duct being connected to one cylinder of the engine. In this way, the inlet duct of the inlet manifold is able to distribute the inlet flow to the various cylinders of the engine. However, the outlet duct furthest away from the inlet of the inlet flow into the inlet duct is at a disadvantage in terms of permeability in relation to the other outlet ducts because they are closer to this inlet. The problem is that the distance that the inlet flow has to cover is longer.
Also known, from document JP 11350963 and document JP 63208616, are inlet manifolds that improve the performance of an engine and give good distribution of the swirl (helicoidal movement of the inlet flow in the cylinder of the engine and the axis of rotation of which is parallel to the axis of the cylinder) through the addition of bosses, ramps or materials in the tracts associated with the cylinders. However, such additions have huge influence over the permeability of the various tracts associated with the various cylinders.